As far as I'm concerned, I don't believe you're allowed to alter a mesh (either that or I don't understand the statement below, 'cause y'know, that happens a lot :P)
Altering Game Files
Do NOT alter any of the decrypted files or codes for the game that might affect the maps and/or gameplay. Giving you an advantage or not, the files should remain intact unless you are given a permission to change them. If you are caught doing this you will most likely face a longer ban.
I'm not to familar with meshes, but I may be able to help. Are you taking the exact ones from the game and just retexturing them? Or are you working with another mesh and you just switched them out? If you are just switching them out, I'd recomend making another meah altogether.
And, (Not sure if this is exact) but if you used Blender to create a whole new mesh, don't you have to convert the file using a mesh converter?
Could yew possibly copy and paste the .mat here? c:
(Sorry I couldn't truely help, I'm just not to good with meshes.)